A new debugger.

Lots of bugs/rough edges/etc - issues will be filed.
Old-style debugging still works (just use --emit_source_annotations to get
the helpful movs back and --break_on_instruction will still fire).

src/xenia/cpu/frontend/ppc_context.h

@@ -246,7 +246,7 @@ enum class PPCRegister {
 };
 
 #pragma pack(push, 8)
-typedef struct alignas(64) PPCContext_s {
+typedef struct PPCContext_s {
   // Must be stored at 0x0 for now.
   // TODO(benvanik): find a nice way to describe this to the JIT.
   ThreadState* thread_state;